A barcode is an example of a symbol information representing various information, in which multiple bars and spaces are alternately arranged. The barcode is used for ID cards in which personal numbers, etc. are recorded in the form of barcodes.
A barcode reader is used to scan the entire surface of such an ID card, take the image in and read a barcode in the image (referring to Patent reference 1). A symbol information reader disclosed in Patent reference 1 acquires the center of gravity position of a symbol labeling map (a barcode map), acquires the left, right, top and bottom edge positions of the barcode symbol on the symbol labeling map, having the center of gravity position as the original point, and detects the position of the barcode symbol.